PROJECT SUMMARY Dietary restriction (DR), the reduction in nutrient intake without malnutrition, has been well documented as a means to extend lifespan and slow age-related diseases in many systems. Because dietary restriction is not easily implemented in humans, the molecules underlying its effects are urgently sought as targets of aging therapeutics. How do we discover these dietary restriction response genes? Against the backdrop of powerful candidate-gene studies by many groups, including ours, a systems-level understanding of dietary restriction in metazoans has been elusive, owing to the dearth of genome-scale screening methods available to date. Furthermore, studies from worms and mice have demonstrated that healthspan measures do not necessarily correlate with lifespan thus arguing whether the lifespan extension of certain nutrient-responsive pathways will necessarily translate to extend healthspan in humans. We propose to meet this challenge with an unbiased screen for genes that mediate the effects of DR on lifespan and healthspan, harnessing the natural genetic variation present in wild outbred individuals. Variation in longevity in wild isolates of flies and mice upon changes in the diet has been shown before but without identifying any associated genes. We propose genetic dissection of the effects of DR on lifespan and age-related decline in mobility in a system that allows expedient confirmation of screen hits. Drosophila melanogaster is the metazoan of choice for this analysis of natural genetic variation, particularly with the advent of sets of wild, genotyped lines for gene mapping by genome-wide association. Our preliminary data make clear that a) effects of DR on lifespan and healthspan differ across different strains of wild flies, b) the effects of DR on healthspan and lifespan are not correlated and c) we can uncover genes necessary for diet-dependent changes in lifespan and healthspan using this approach. We propose the following aims to discover and characterize genes that underlie this variation: (1) we will identify candidate genes that explain the underlying differences between wild strains in lifespan and age-related climbing ability upon DR; (2) we will test candidate genes identified to mediate the genetic basis of differences in lifespan and age-related climbing ability under different diets and (3) we will characterize the potential mechanisms by which some of the identified genes extend healthspan and lifespan and the relationship between these two traits. With the completion of these Aims, we will have enabled the discovery of nucleotides, genes, and pathways by which dietary restriction affects lifespan and healthspan, and the relationship between the two in the fly. These molecules will open up the potential for long-term studies in the field by providing novel targets for healthspan and lifespan extension in mammals.